Patterns of Progression in Metastatic Estrogen Receptor Positive Breast Cancer: An Argument for Local Therapy

Purpose. Despite advances in endocrine therapy (ET), metastatic estrogen receptor positive breast cancer (BrCA) remains incurable. Though the mechanisms of resistance to ET have been studied extensively, the anatomic pattern of disease progression remains poorly characterized. The purpose of this study was to characterize the pattern of progression for patients receiving ET for metastatic BrCA. Methods. The records of 108 patients with metastatic BrCA who progressed on ET were reviewed. Progression was characterized as follows: diffuse progression, progression in greater than 3 sites; oligoprogression, progression in fewer than 3 sites with prior diffuse metastases; and oligometastatic disease with progression, progression in 3 or fewer sites with prior limited metastases. Results. Seventy-four patients (69%) displayed only diffuse disease progression. Conversely, 23 patients (21%) displayed oligoprogression and 11 patients (10%) displayed oligometastases with progression at least once in their disease course. Further analysis of the patients with oligoprogression suggested that in 14 patients the sites of progression would have been amenable to local therapy. Conclusion. Oligoprogressive disease occurs in a significant subset of patients with metastatic BrCA treated with ET. These patients with oligoprogressive disease may be eligible for local therapy, potentially obviating the need to change of systemic therapy.